Transient-Promoter-Stabilized NiFe Oxyhydroxide Enables Durable kW-Scale Water Splitting Under Fluctuating Power

Renewable-powered water electrolysis provides a carbon-neutral route to hydrogen, yet large-scale deployment is constrained by reliance on stable but carbon-intensive grid electricity. Direct integration with fluctuating renewable power requires catalysts and devices that can endure dynamic operating conditions. Here we present a transient-promoter strategy for NiFe oxyhydroxide oxygen evolution reaction (OER) catalysts, realized from Ni₃Fe_1.2Cr_0.8O_x precursor, for kilowatt-scale anion exchange membrane water electrolyzers (AEMWEs). Ex situ and operando spectroscopy establish that Cr (i) modulates Ni/Fe oxidation states to enrich positive charge and facilitate oxyhydroxide formation, (ii) induces porosity that enhances electrolyte penetration and OH^- adsorption, and (iii) leaches sacrificially to protect Ni/Fe active sites. Lab-scale AEMWE device achieves an industrially relevant current density of 1 A cm^{- 2} at a cell voltage of 1.68 V and sustains continuous operation for over 30 days under both constant and fluctuating loads. Scaling from 1 cm² AEMWE to an 8-cell, 512 cm² stack, the system can handle an electrical power of 2.5 kW at peak, and delivers 1 A cm^{- 2} at 1.78 V per cell at 60 °C. The stack remains resilient over 13 simulated solar cycles (>50 h), underscoring the feasibility of integrating renewable electricity with durable, NiFe oxyhydroxide OER catalyst based AEMWEs.